Electrical service providers such as electrical utilities employ electricity meters to monitor energy consumption by customers (or other entities). Electricity meters track the amount of energy consumed a load (e.g. the customer), typically measured in kilowatt-hours (“kwh”), at each customer's facility. The service provider uses the consumption information primarily for billing, but also for resource allocation planning and other purposes.
Electrical power is transmitted and delivered to load in many forms. For example, electrical power may be delivered as polyphase wye-connected or delta-connected power or as single phase power. Such various forms are known as service types. Different standard electricity meter types, known as meter forms, are used to measure the power consumption for the various service types. The commonly used meter forms in the United States include those designated as 2S, 3S, 5S, 45S, 6S, 36S, 9S, 16S, 12S and 25S meter forms, which are well known in the art.
Electrical service providers have historically billed for electrical service in arrears, using information stored within the electricity meter to determine the amount of each invoice. In a typical operation, the electricity meter stores a value representative of the amount of energy consumed in a mechanical or electronic accumulation register. From time to time, the electrical service provider obtains the value of the register and bills the customer accordingly. For example, a meter reader employed by the service provider may, each month, physically read the register value off a meter display. The service provider then employs the obtained register value to determine the amount of electricity consumed over the month and bills the customer for the determined amount.
A problem with the above-described operation of electrical service providers arises from the fact that some customers are frequently delinquent in or, in default of, payments for electricity consumption. Because electrical service is billed in arrears, delinquent payments can result in significant losses for the service provider.
In addition, interrupting the delivery of electrical power has historically been an expensive and significant event. Typically, a technician must be dispatched to the customer's residence, or in the vicinity thereof, to physically disconnect the power. Accordingly, while the electrical service provider might physically disconnect the power to the customer's facility for several months of complete payment default, physical disconnection is not practical in circumstances in which customers are merely delinquent, or that can only pay portions of their bills. In particular, the cost an effort of sending a technician out to disconnect electrical service is wasted if the customer pays a day or two later, thereby requiring another service call to restore service.
One method of controlling losses associated with delinquent customers is to require prepayment for services. In prepayment arrangements, customers use prepaid debit cards or credit cards to “purchase” energy in advance. When the purchased energy has been consumed, the electrical service is disconnected. Thus, the service provider is not exposed to extended periods of electrical service for which no payment may be provided. Another method of handling delinquent customers is to intermittently interrupt power to delinquent customers until the past due payments are made. Intermittent interruptions tend to reduce the amount of energy consumed by the delinquent payor, thus advantageously reducing utility provider losses while also reducing bills to the delinquent payor.
Each of the above methods, however, typically requires the ability to disconnect and/or reconnect the customer's power without a technician service call to the customer's location. For example, in a prepayment scenario, the service provider must have a method of disconnecting power once the prepaid amount of energy has been consumed. Similarly, the intermittent interruption technique requires frequent connection and disconnection of the electrical service.
One technique for automated or remote service disconnection is to employ a service disconnect switch device within an electricity meter. The service disconnect switch is a relay or other device that controllably disconnects and re-connects the utility power lines to the customer's feeder lines, thereby controllably interrupting power to the customer's facility. In some cases, the service disconnect switch is tripped by a remote device that communicates with the electricity meter circuitry through a modem, radio or the like. Alternatively, such as in the case of prepayment, the meter itself may be programmed to disconnect and reconnect electrical service under certain circumstances. In some situations, the meter may disconnect and restore electrical service through a combination of local programming and remote commands.
Thus, the inclusion of a service disconnect switch within a meter facilitates various methods and techniques for providing electrical service to parties that have poor payment records. Such methods and techniques advantageously do not require a permanent disconnection by a field technician. The conveniences provided by a service disconnect switch also extends beyond use in connection with delinquent payors. For example, electrical energy rationing may be implemented using techniques enabled by the service disconnect switch.
Nevertheless, various issues that arise from the use of a service disconnect switch have not been adequately addressed in the prior art. For example, many of the above described service interruption techniques typically require automated reconnection to be truly viable. In other words, if a technician must be dispatched every time power is to be reconnected to a customer after a service interruption, the convenience and cost advantages of the automated disconnection are significantly reduced.
Automatic reconnection of a customer's facility to electrical service can raise potential dangers. For example, consider a situation in which the customer is operating a clothes iron or electric stove when electrical service is disconnected. If the customer does not remember to turn such a device off during the electrical service interruption, then the device will automatically resume operating (at high temperatures) when power is restored. The automatic restoration of iron or stove operation can create a fire hazard, particularly if the customer has since become otherwise occupied or has left the premises. Accordingly, restoring power through an automatically operated service disconnection switch raises some safety issues, as well as other issues.
In addition to safety issues, a drawback of service disconnect switches is that they may be defeated through tampering either within or external to the meter. Such tampering typically involves placing a bypass around the service disconnect switch. The bypass provides a path through which the customer may receive electrical power even though the service disconnect switch has been opened.
One prior art device disclosed in U.S. Pat. No. 5,940,009 detects such tampering by detecting a voltage signal on the load-side connection of a disconnect switch. In particular, this prior art device connects the load-side customer feeder lines to a processor through a voltage divider. The processor then interprets the waveforms of from multiple feeder lines to determine whether power is still being provided to the load even when a service disconnect switch has disconnected the service to the customer's load. The drawback of the device disclosed in U.S. Pat. No. 5,940,009 is that it requires multiple inputs to a microprocessor to monitor multiple feeder lines, and further exposes the microprocessor directly to the power line signals, albeit through a voltage divider.
Other issues with service disconnect devices within meters include whether and how a disconnect switch could be implemented in a modular meter. Modular meters are those that include separable components. One removable component includes much of the meter electronic and processing circuitry while the other component contains high voltage sensor circuitry that interconnects with the power lines. Modular meters allow for easy enhancement of meter features and operations because replacement of the removable component that includes the meter electronic and processing circuitry typically suffices for such enhancements. Thus, to obtain improved functionality, only a portion of the meter must be replaced. Service disconnect switches do not readily lend themselves to modular meters because service disconnect switches require both electronic and high power components, which are typically separated into different modules of the modular meter.
There is a need, therefore, for an electricity meter that employs service disconnect switch and that avoids one or more of the above described drawbacks. In particular, a need exists for an electricity meter that includes a service disconnect switch having increased safety enhancements associated with reconnecting a customer's electrical service after an interruption. A need exists for an electricity meter that obtains the benefits of both modularity in a meter and the use of an automatically operated service disconnect switch within a meter.